JPWO2012157570A1 - Wireless transmission apparatus and wireless transmission method - Google Patents

Abstract

The wireless transmission device receives a radio frame that is multiplexed with a LAN signal including a timing packet and an error detection code and converted into a radio output signal from the radio transmission path, demodulates the radio frame, and generates a radio frame from the error detection code in the radio frame. A radio receiving unit that detects a signal error and calculates a radio frame error rate, and a timing reproduction mode that outputs a clock and a timing pulse at a period and a phase that are reproduced from the timing packet when the radio frame error rate exceeds a threshold value. A holdover switching unit that switches to a holdover mode that outputs a clock and a timing pulse at a cycle and phase stored in a normal state.

Description

  The present invention relates to a wireless transmission device and a wireless transmission method.

  In a wireless transmission device having a function of receiving a timing packet of IEEE 1588 Precision Time Protocol (see Non-Patent Document 1) and reproducing the clock frequency and time, when a timing packet is discarded due to a signal error in the wireless and packet transmission paths, It is necessary to prevent the deterioration of the synchronization accuracy of the clock frequency and time by extending the correction period. For this reason, when an abnormality occurs in a device or a transmission line, and reception of a timing packet is impossible or an extension of the reception period occurs, the wireless transmission device switches the synchronization information from the timing reproduction mode to the holdover mode. The clock frequency with the master station that is the source and the speed of the time shift are kept within a certain value.

  Here, the timing reproduction mode is a mode in which a clock and a timing pulse are output using a period and a phase reproduced based on a timing packet received at the present time. The holdover mode is a mode in which a clock and a timing pulse are output using a period and a phase saved from a timing pulse that has been successfully received in the past. Switching from the timing reproduction mode to the holdover mode is performed based on the reception normality of the timing packet or a timeout.

IEEE 1588 Precision Time Protocol

  Generally, as a method of synchronizing clock frequencies and times of a plurality of devices using a burst signal such as a packet having no synchronization information, IETF Network Time Protocol (NTP) or IEEE 1588-2002 Precision Time Protocol (PTP) verison . 1, ITU-TG 8282 / Y. There are standards such as 1362 Synchronous Ethernet (registered trademark) and Pseudo Wire Emulsion Edge to Edge (PWE3).

  Also, standards such as Time Division Duplex Long Evolution (TDD LTE) that require time synchronization between radio transmission apparatuses in addition to frequency, and that require high accuracy such as frequency in ppb units and time phase accuracy in units of us. For IEEE 1588-2008 PTP version. 2 or individual devices could only be synchronized to Global Navigation Satellite Systems (GNSS).

  Further, when a packet signal is transmitted through a wireless transmission path, the timing packet reception period is extended and the reproduction clock frequency and time are increased by discarding the packet due to a signal error that occurs intermittently due to equipment failure and worsening weather. Deterioration of accuracy is a problem.

  As a method for solving this problem, ITU-T Y.T. 1731 and a method of executing EOAM (Ethernet (registered trademark) OAM) control as defined by IEEE 802.1ag. In this method, it is possible to detect a transmission line abnormality including a device failure at a high speed by using continuous monitoring (continuity check) using an EOAM signal. ITU-T G. 8032 / Y. In 1344 Ethernet (registered trademark) Ring Protection Switching, Continuity Check is proposed as an example of a method for detecting an abnormality of a ring transmission path including a device failure at high speed.

  FIG. 5 is a block diagram illustrating a configuration of a system including a wireless transmission device. In FIG. 5, the wireless transmission device 40 c includes an EOAM unit 49. Further, the wireless transmission device 20 c that is a wireless opposite station of the wireless transmission device 40 c also includes the EOAM unit 21 similar to the EOAM unit 49. The EOAM unit 49 transmits and receives an EOAM signal to and from the packet switch unit 42. That is, the EOAM unit 49 transmits / receives control packets in a short cycle via the packet switch unit 42 to / from the wireless transmission device 20c, which is a wireless opposite station, in all packet transmission paths including the wireless transmission path 30. Here, the EOAM unit 49 determines that the wireless transmission device 20c or the transmission path is abnormal when packet reception is interrupted for a certain period.

  The EOAM signal is not limited to the continuity check, but the description will be continued by taking the continuity check as an example in order to simplify the description. The EOAM unit 49 uses the continuity check packet transmitted from the EOAM unit 21 of the radio transmission device 20c, which is a radio opposite station, to determine “normal” if a correct control packet can be received within a specific period. On the other hand, if the correct control packet cannot be received within a specific period, the EOAM unit 49 determines “abnormal”, detects an abnormality in the device or the transmission path based on the packet, and determines the result as a radio interval normal determination signal. Is output to the holdover switching unit 46. By outputting the continuity check packet in a short cycle from the EOAM unit 21 of the radio transmission device 20c, the radio transmission device 40c can detect the discard of the continuity check control packet at a high speed by the EOAM unit 49.

  Further, the holdover switching unit 47 switches the operation from the timing regeneration mode to the holeover mode when the EOAM unit 49 detects an abnormality in the device or the transmission path. The period of the control packet is ITU-T Y. 1731 or IEEE 802.1ag recommendation.

  However, the EOAM unit has a problem that the price is high and the processing load for executing the EOAM control is also high. In addition, depending on the weather (rainfall, snowfall, sandstorm, etc.), the radio transmission path may cause a decrease in radio reception power and an increase in phase noise, resulting in errors in the signal, leading to the discard of radio frames and timing packets. is there. From this, regarding the normality of the received timing packet and the detection of an abnormal state due to timeout, in the wireless transmission device, switching to holdover is delayed, resulting in a large shift in clock frequency and time. There's a problem.

  The present invention has been made in view of the above points, and without performing EOAM control, an abnormal state is detected in a short time after an abnormality has occurred in a device or a transmission line, and the clock frequency and time An object of the present invention is to provide a wireless transmission device and a wireless transmission method capable of maintaining accuracy.

  A wireless transmission apparatus according to the present invention is made to solve the above-described problem. A wireless frame in which a LAN signal including a timing packet and an error detection code are multiplexed and converted into a high-frequency wireless output signal is provided. The radio frame error rate is calculated by receiving and demodulating from the radio transmission path, separating the LAN signal from the demodulated radio frame, and detecting a radio frame signal error from the error detection code in the radio frame. When the radio frame error rate calculated by the radio receiver and the radio receiver exceeds a first threshold, the clock and timing pulse are generated based on the period and phase reproduced from the timing packet included in the LAN signal. From the timing playback mode to be output, it is based on the cycle and phase saved during normal operation. Tsu to click and holes over mode for outputting timing pulses, a radio transmission apparatus characterized by comprising, a holdover switching unit for switching the operation mode.

  The wireless transmission method according to the present invention is a wireless transmission method in a wireless transmission device, in which a wireless receiver multiplexes a LAN signal including a timing packet and an error detection code, and converts the multiplexed signal into a high-frequency wireless output signal. A radio frame is received and demodulated from a radio transmission path, a LAN signal is separated from the demodulated radio frame, and a signal error of the radio frame is detected from an error detection code in the radio frame. And when the radio frame error rate calculated by the radio reception unit exceeds a first threshold, the holdover switching unit sets the period and phase reproduced from the timing packet included in the LAN signal. From the timing recovery mode that outputs the clock and timing pulse based on normal The hole over mode for outputting the clock and timing pulses on the basis of the period and phase which has been exist, a radio transmission method characterized by comprising the steps of: switching the operating mode.

  According to the first embodiment of the present invention, a radio frame is demodulated from a radio output signal received from a radio transmission path, a radio frame error rate is calculated from an error detection code in the demodulated radio frame, and the radio frame error is calculated. When the rate exceeds the first threshold, the timing reproduction mode is shifted to the hole over mode. Thereby, the wireless transmission device can detect the abnormal state in a short time after the occurrence of the abnormality in the device or the transmission line without executing the EOAM control, and can maintain the accuracy of the clock frequency and the time.

It is a block diagram which shows the structure of the system provided with the radio | wireless transmission apparatus concerning 1st embodiment of this invention. It is a flowchart for demonstrating the normal determination procedure of the timing packet of a timing process part and a receiving interval in 1st embodiment of this invention. It is a flowchart for demonstrating the holdover determination procedure of the holdover switching part in 1st embodiment of this invention. It is a block diagram which shows the structure of the system provided with the wireless transmission apparatus in 2nd embodiment of this invention. It is a block diagram which shows the structure of the system provided with the radio | wireless transmission apparatus.

[First embodiment]
A first embodiment of the present invention will be described in detail with reference to the drawings.
In the first embodiment of the present invention, in the wireless transmission device that receives the timing packet of IEEE 1588 Precision Time Protocol (hereinafter referred to as “IEEE 1588 PTP”) and reproduces the clock frequency and time, the wireless transmission device In addition to the normality determination, the wireless and packet transmission path normality determination is performed. As a result, the wireless transmission device shifts to the holdover mode in a short time after the occurrence of an abnormality in the device or the transmission path, and can maintain the accuracy of the clock frequency and the time.

  FIG. 1 is a block diagram illustrating a configuration of a system including a wireless transmission device. The user network 10 includes a transmission device (not shown) used by the user and a master station (not shown) serving as a synchronization information source of IEEE 1588 PTP. The LAN signal from the master station in the user network 10 includes both user data from the user network 10 and a timing packet used for IEEE 1588 PTP synchronization. The wireless transmission device 20a receives a LAN signal from the user network 10, multiplexes the LAN signal into a wireless frame, and further multiplexes an error detection code. Further, the wireless transmission device 20a performs analog modulation and frequency conversion on a wireless frame in which the LAN signal and the error detection code are multiplexed, and generates a high-frequency wireless output signal. Further, the wireless transmission device 20 a outputs the generated wireless output signal to the wireless transmission path 30.

  The wireless transmission device 40a includes a wireless reception unit 41a, a packet switch unit 42, a timing processing unit 43, a time counter unit 44, a holdover unit 45, a holdover switching unit 46, a time counter oscillator 47, a hold An over-oscillator 48.

  The wireless reception unit 41a receives a wireless output signal transmitted through the wireless transmission path 30, performs frequency conversion and digital demodulation on the received wireless output signal, and obtains a wireless frame. Further, the wireless reception unit 41a separates the LAN signal from the obtained wireless frame, and outputs the separated LAN signal to the packet switch unit 42 as a separated LAN signal. In addition, the wireless reception unit 41a measures the received power of the received wireless output signal, and outputs the measured received power to the holdover switching unit 46 as a received power signal. The radio reception unit 41a calculates a radio frame error rate by detecting a radio frame signal error from an error detection code in the radio frame, and uses the calculated radio frame error rate as a radio frame error signal to hold over. Output to the switching unit 46.

  The packet switch unit 42 is a layer 2 switch that specifies and outputs a transfer destination port from each field value in a packet defined by IEEE 802.3. The packet switch unit 42 receives the separated LAN signal output from the wireless reception unit 41a, detects a timing packet used for clock frequency and time synchronization according to IEEE 1588 PTP in accordance with the recommendation of IEEE 1588 PTP, and detects the detected timing packet Is output to the timing processing unit 43 as a timing packet signal. Further, the packet switch unit 42 outputs to the user network 50 a LAN signal other than the timing packet addressed to its own station (wireless reception unit 41a). Further, the packet switch unit 42 detects a signal error (packet error) based on the redundant code included in the packet of the received separated LAN signal, calculates a packet error rate, and performs holdover switching as a packet error signal. To the unit 46.

  The timing processing unit 43 receives the timing packet signal output from the packet switch unit 42. The timing processing unit 43 acquires the clock frequency, time, and propagation delay of the master station serving as a synchronization information source in IEEE 1588 PTP from the received timing packet signal. In addition, the timing processing unit 43 outputs a correction signal for synchronizing the time counter 44 to the time of the master station to the time counter unit 44 as a counter correction signal. The timing processing unit 43 performs normal determination of the timing packet according to a predetermined determination procedure, and outputs the result to the holdover switching unit 46 as a timing packet normal determination signal.

  The time counter unit 44 operates the counter using the time counter operation clock signal output from the time counter oscillator 47, and corrects the counter value offset and the count cycle based on the counter correction signal output from the timing processing unit 43. To do. Thereby, the time counter unit 44 synchronizes the counter of the time counter unit 44 with the time counter of the master station. The time counter unit 44 outputs the clock and timing pulse generated from the counter of the time counter unit 44 synchronized with the time of the master station to the holdover unit 45 as a synchronization timing signal.

  The holdover unit 45 receives the synchronization timing signal output from the time counter unit 44 and the holdover operation clock signal output from the holdover oscillator 48, and uses the holdover operation clock signal to generate a synchronization timing signal. The period and phase information is stored.

  The holdover unit 45 operates based on the holdover switching signal output from the holdover switching unit 46. Specifically, in the timing recovery mode, the holdover unit 45 generates a clock and a timing pulse based on the period and phase recovered from the synchronization timing signal, and the generated clock and timing pulse are output to the synchronization timing pulse output signal. To the user network 50. On the other hand, in the holdover mode, the holdover unit 45 generates a clock and timing pulse based on the period and phase stored in the normal state, and uses the generated clock and timing pulse as a synchronization timing pulse output signal as a user network. Output to 50.

  The time counter oscillator 47 outputs a counter operation clock signal to the time counter unit 44. The holdover oscillator 48 outputs a holdover operation clock signal to the holdover unit 45.

  The holdover switching unit 46 receives the received power signal and the radio frame error signal output from the radio receiving unit 41a, the packet error signal output from the packet switch unit 42, and the imming packet normality determination output from the timing processing unit 43 Each of the signals is received.

  The holdover switching unit 46 determines whether to use the timing regeneration mode or the holdover mode according to a predetermined determination procedure (described later with reference to FIG. 3). The holdover switching unit 46 outputs a holdover switching signal indicating the determination result to the holdover unit 45.

Next, the operation procedure of the wireless transmission device 40a of this embodiment will be described.
As an outline of the operation procedure, the wireless receiver 41a of the wireless transmission device 40a receives a wireless output signal from the wireless transmission path 30, performs frequency conversion and digital demodulation, and obtains a wireless frame. Then, the wireless reception unit 41a separates the packet signal from the obtained wireless frame, and outputs the separated packet signal to the packet switch unit 42 as a separated LAN signal. Further, the wireless reception unit 41a measures the reception power of the wireless output signal, and outputs the measured reception power to the holdover switching unit 46 as a reception power signal. Further, the radio reception unit 41a detects a radio frame signal error from the error detection code in the radio frame, detects it, and outputs the signal error as a radio frame error signal to the holdover switching unit 46.

  The packet switch unit 42 receives the separated LAN signal output from the wireless reception unit 41a. Then, the packet switch unit 42 detects a timing packet used for clock frequency and time synchronization by IEEE 1588 PTP, and outputs the detected timing packet to the timing processing unit 43 as a timing packet signal. Further, the packet switch unit 42 outputs to the user network 50 as a LAN output signal other than the timing packet addressed to its own station (wireless reception unit 41a). Further, the packet switch unit 42 detects a signal error based on the redundant code in the packet of the separated LAN signal, and outputs the detected signal error to the holdover switching unit 46 as a packet error signal.

  The timing processing unit 43 receives the timing packet signal output from the packet switch unit 42. The timing processing unit 43 obtains the clock frequency, time, and propagation delay from the received timing packet signal from the master station that is a synchronization information source in IEEE 1588 PTP, and the time (counter) of the time counter unit 44 and the master station A correction signal for synchronizing the two is output to the time counter unit 44 as a counter correction signal. Further, the timing processing unit 43 performs normal determination of the timing packet and the reception interval according to a predetermined determination procedure (described later with reference to FIG. 3), and sends the result as a timing packet normal determination signal to the holdover switching unit 46. Output.

  FIG. 2 is a flowchart for explaining a normal determination procedure of the timing packet and the reception interval of the timing processing unit. First, the timing processing unit 43 calculates the propagation delay of the packet from a specific field in the timing packet, and compares the obtained propagation delay with predetermined thresholds D and F (step S1).

  When the propagation delay of the timing packet is not less than the threshold value D and not more than the threshold value F (step S1-YES), the timing processing unit 43 extracts a time stamp representing the time counter value of the master station from a specific field in the timing packet. Then, the timing processing unit 43 calculates the absolute value of the difference between the extracted time stamp and the time counter value of the local station (wireless receiving unit 41a), and compares the calculated absolute value of the difference with the threshold G (step S1). S2).

  When the absolute value of the difference between the extracted time stamp and the time counter value of the local station (wireless reception unit 41a) is equal to or less than the threshold G (step S2-YES), the timing processing unit 43 calculates the calculated timing packet arrival interval. Then, a predetermined threshold value H is compared (step S3). When the timing packet arrival interval is equal to or less than the threshold value H (step S3-YES), the timing processing unit 43 determines normal detection (step S4).

  On the other hand, when the propagation delay of the timing packet is not equal to or greater than the threshold value D or not equal to or less than the threshold value F in step S1 (step S1-NO), the timing processing unit 43 determines that an abnormality has been detected (step S5). In step S2, if the absolute value of the difference between the extracted time stamp and the time counter value of the local station (wireless reception unit 41a) is not less than or equal to the threshold G (step S2-NO), the timing processing unit 43 detects the abnormality. (Step S5). In step S3, if the timing packet arrival interval is not equal to or less than the threshold value H (step S3-NO), the timing processing unit 43 determines that an abnormality has been detected (step S5).

  In this way, the timing processing unit 43 performs normal determination of the timing packet according to the determination procedure shown in FIG. 2 based on the received timing packet.

Returning to FIG. 1, the description of the configuration is continued. The time counter unit 44 operates the counter using the time counter operation clock signal output from the time counter oscillator 47.
Furthermore, the time counter unit 44 synchronizes the counter with the time of the master station by correcting the offset of the counter value and the count cycle based on the counter correction signal output from the timing processing unit 43. The time counter unit 44 outputs the clock and timing pulse generated from the counter synchronized with the master station to the holdover unit 45 as a synchronization timing signal.

  The holdover unit 45 stores the period and phase information of the synchronization timing signal output from the time counter unit 44 using the holdover operation clock signal output from the holdover oscillator 48. Further, the holdover unit 45, based on the holdover switching signal output from the holdover switching unit 46, in the timing reproduction mode, uses the clock and timing pulse as the synchronization timing pulse output signal as the synchronization timing pulse output signal. Output to the network 50. On the other hand, in the holdover mode, the holdover unit 45 generates a clock and timing pulse having a period and a phase that are stored in a normal state, and outputs them as a synchronous timing pulse output signal.

  The holdover switching unit 46 receives the reception power signal and radio frame error signal output from the radio reception unit 41a, the packet error signal output from the packet switch unit 42, and the timing packet normality determination signal output from the timing processing unit 43. Receive each one. Further, the holdover switching unit 46 determines whether it is the timing regeneration mode or the holdover mode according to predetermined control, and outputs the determination result to the holdover unit 45 as a holdover switching signal.

  FIG. 3 is a flowchart for explaining the holdover determination procedure of the holdover switching unit. The holdover switching unit 46 detects wireless reception power from the reception power signal, and compares the detected reception power with a predetermined threshold A (first threshold) (step Sa1).

  If the received power detected from the received power signal is greater than or equal to the threshold A (step Sa1-YES), the holdover switching unit 46 calculates the error rate of the radio frame from the radio frame error signal, and calculates the error rate of the calculated radio frame. And a predetermined threshold value B (second threshold value) are compared (step Sa2).

  When the error rate of the radio frame rate is equal to or higher than the threshold value B (step Sa2-YES), the holdover switching unit 46 calculates the error rate of the packet signal from the packet error signal, and the calculated error rate and a predetermined error rate are determined. The threshold value C (third threshold value) is compared (step Sa3).

  When the error rate of the packet signal is equal to or higher than the threshold value C (step Sa3-YES), the holdover switching unit 46 determines whether or not the timing packet has been normally received based on the timing packet normality determination signal (step Sa4). When the timing packet is normally received (step Sa4-YES), the holdover switching unit 46 switches to the timing reproduction mode (step Sa5).

  On the other hand, in step Sa1, when the received power detected from the received power signal is not equal to or greater than the threshold A (step Sa1-NO), the holdover switching unit 46 switches to the holdover mode (step Sa6). In Step Sa2, when the error rate of the radio frame rate is not equal to or higher than the threshold value B (Step Sa2-NO), the holdover switching unit 46 switches to the holdover mode (Step Sa6).

  In step Sa3, when the error rate of the packet signal is not equal to or higher than the threshold value C (step Sa3-NO), the holdover switching unit 46 switches to the holdover mode (step Sa6). In Step Sa4, when the timing packet is not normally received (Step Sa4-NO), the holdover switching unit 46 switches to the holdover mode (Step Sa6).

  Thus, when the received power is greater than or equal to the threshold A, the radio frame error rate is greater than or equal to the threshold B, the packet error rate is greater than or equal to the threshold C, and the timing packet normal reception conditions are all satisfied, the holdover switching unit 46 Then, the mode is switched to the timing reproduction mode, and the clock and timing pulse are output at the period and phase reproduced based on the timing packet. On the other hand, if any one of the conditions is not satisfied, the holdover switching unit 46 switches to the holdover mode, and outputs a clock and a timing pulse with a period and a phase that are stored in a normal state.

  As described above, the wireless transmission device 40a receives the radio frame from the radio transmission path 30 and demodulates the radio frame that is multiplexed with the LAN signal including the timing packet and the error detection code and converted into the radio output signal of high frequency, The radio signal is calculated by the radio receiving unit 41a and the radio receiving unit 41a that separates the LAN signal from the demodulated radio frame and detects a radio frame signal error from the error detection code in the radio frame to calculate the radio frame error rate. When the received radio frame error rate exceeds the threshold B, it is stored in a normal state from the timing recovery mode in which the clock and timing pulse are output based on the period and phase recovered from the timing packet included in the LAN signal. A clock and timing pulse output based on period and phase The over mode comprises a holdover switching unit 46 for switching the operation mode, the.

  With this configuration, the radio frame is demodulated from the radio output signal, the radio frame error rate is calculated from the error detection code in the demodulated radio frame, and when this radio frame error rate exceeds the threshold B, the timing reproduction is performed. Switch from mode to holeover mode. As a result, the wireless transmission device 40a can detect an abnormal state in a short time after the occurrence of an abnormality in the device or the transmission line without executing the EOAM control, and shift to the holdover mode. The accuracy of frequency and time can be maintained. Further, the wireless transmission device 40a need not include a compensation oscillator.

  Further, the wireless reception unit 41a measures the reception power of the wireless output signal received from the wireless transmission path 30, and the holdover switching unit 46, when the reception power measured by the wireless reception unit 41a falls below the threshold A, The operation mode is switched from the timing reproduction mode to the hole over mode.

  With this configuration, when the received power of the wireless output signal is measured and the received power falls below the threshold A, the timing regeneration mode is switched to the hole over mode. As a result, the wireless transmission device 40a can shift to the holdover mode in a short time after the occurrence of an abnormality in the device or the transmission line without executing EOAM control, and maintains the accuracy of the clock frequency and the time. be able to.

  In addition, the wireless receiver 41a detects a timing packet used for clock frequency and time synchronization from a LAN signal separated from a wireless frame, and detects a signal error based on a redundant code in the packet of the LAN signal. The packet switch unit 42 for calculating the packet error rate is provided, and the holdover switching unit 46 switches from the timing regeneration mode to the hole over mode when the packet error rate calculated by the packet switch unit 42 exceeds the threshold C. Switch.

  With this configuration, when a signal error is detected based on the redundant code in the packet of the LAN signal, the packet error rate is calculated, and when the packet error rate exceeds the threshold C, the timing recovery mode is switched to the hole over mode. Switch. As a result, the wireless transmission device 40a can shift to the holdover mode in a short time after the occurrence of an abnormality in the device or the transmission line without executing EOAM control, and maintains the accuracy of the clock frequency and the time. be able to.

  Further, the holdover switching unit 46 determines that the radio frame error rate is equal to or lower than the threshold value B, the received power is equal to or higher than the threshold value A, the packet error rate is equal to or lower than the threshold value C, and the timing packet normal reception conditions are all satisfied. The operation mode is switched from the hole over mode to the timing reproduction mode.

  With this configuration, when the radio frame error rate is equal to or less than the threshold value B, the reception power is equal to or greater than the threshold value A, the packet error rate is equal to or less than the threshold value C, and the timing packet normal reception conditions are all satisfied, the timing regeneration mode is Switch to. Accordingly, the wireless transmission device 40a can accurately perform the transition between the hole over mode and the timing reproduction mode without executing the EOAM control, and can maintain the accuracy of the clock frequency and the time.

[Second Embodiment]
A second embodiment of the present invention will be described in detail with reference to the drawings.
The second embodiment is different from the second embodiment in that an adaptive modulation scheme is adopted in the wireless transmission device and in that the holdover transition condition is devised. Only the differences from the first embodiment will be described below.

FIG. 4 is a block diagram illustrating a configuration of a system including a wireless transmission device. The wireless transmission device 20b and the wireless transmission device 40b are wireless transmission devices that employ an adaptive modulation scheme.
Here, the adaptive modulation scheme is to perform the maximization of the feasible band according to the radio reception power, and to switch to a modulation scheme having a high tolerance against disturbance due to power and noise when the reception power is reduced due to bad weather or the like. It is a method. Note that a predetermined algorithm may be appropriately used for the adaptive modulation method itself.

  The wireless transmission device 40b includes a wireless reception unit 41b. The wireless reception unit 41b receives a wireless output signal from the wireless transmission device 20b, which is a wireless opposite station, via the wireless transmission path 30. The radio reception unit 41b detects radio modulation scheme switching based on the modulation scheme information stored in the radio frame, and outputs it to the holdover switching unit 46 as an AMR (Adaptive Modulation Radio) switching signal. In addition to the determination procedure described with reference to FIG. 3, the holdover switching unit 46 detects switching of the radio modulation scheme based on the AMR switching signal. The holdover switching unit 46 switches the operation mode to the holdover mode for a certain time when the radio modulation scheme is switched. When this switching is stable for a certain time, the holdover switching unit 46 switches the operation mode to the timing reproduction mode.

  As described above, the wireless transmission device 20b and the wireless transmission device 40b are wireless transmission devices employing an adaptive modulation scheme. The holdover switching unit 46 of the wireless transmission device 40b switches the operation mode to the hole-over mode for a certain time when the modulation method is switched by the adaptive modulation, and further sets the operation mode when the modulation method is stable for a certain time. Switch to playback mode.

  With this configuration, when switching of the modulation method by adaptive modulation occurs, the operation mode is switched to the hole-over mode for a certain time, and when the modulation method is stabilized for a certain time, the operation mode is switched to the timing reproduction mode. As a result, the wireless transmission device 40b can shift to the holdover mode in a short time after an abnormality occurs in the device or the transmission line without executing EOAM control, and the clock frequency and time accuracy can be improved. Can keep.

  Here, the timing packet may be a timing packet used for clock frequency and time synchronization according to IEEE 1588 Precision Time Protocol.

  Note that when the clock frequency and time are reproduced by IEEE 1588 PTP, it is necessary to correct the propagation delay of the timing packet. However, in the IEEE 1588-compliant method, the delay measurement is performed using the timing packet itself, so that the delay update period The modulation scheme can be switched in a short period of a radio frame unit, that is, in the adaptive modulation scheme in which the propagation delay changes, there is a possibility that the delay correction becomes insufficient and the error to the reproduction clock frequency and time increases. .

  Even in this case, the wireless transmission device 40b detects the switching of the modulation method by the adaptive modulation method in addition to the detection of the wireless transmission path abnormality including the device failure and the packet communication abnormality, thereby causing the operation mode to be changed. Switch to holdover mode. Thereby, the wireless transmission device 40b can keep the error of the clock frequency and the time small.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

  For example, in the above description, the transmission function of the wireless transmission device 20a and the function blocks for passing signals from the user network 50 to the user network 10 are not shown. Even if the functional block is added and the wireless transmission device 20a includes a functional block for reproducing the clock frequency and time, the gist of the present invention does not depart.

  Note that a program for realizing the wireless transmission device described above may be recorded on a computer-readable recording medium, and the program may be read into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included. The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, what is called a difference file (difference program) may be sufficient.

(Additional remark 1) The said timing packet is a timing packet used for the clock frequency and time synchronization by IEEE1588 Precision Time Protocol, The wireless transmission apparatus characterized by the above-mentioned.

(Supplementary note 2) A wireless transmission method characterized in that the timing packet includes a step of using the timing packet for clock frequency and time synchronization according to IEEE 1588 Precision Time Protocol.

  This application claims priority on May 18, 2011 based on Japanese Patent Application No. 2011-111124 for which it applied to Japan, and uses the content here.

  Provided are a wireless transmission device and a wireless transmission method capable of detecting an abnormal state in a short time after an abnormality has occurred in a device or a transmission line without executing EOAM control and maintaining the accuracy of a clock frequency and a time. be able to.

10 user network 20a wireless transmission device 20b wireless transmission device 20c wireless transmission device 21 EOAM unit 30 wireless transmission path 40a wireless transmission device 40b wireless transmission device 40c wireless transmission device 41a wireless reception unit 42 packet switch unit 43 timing processing unit 44 time counter unit 45 Holdover section 46 Holdover switching section 47 Time counter oscillator 48 Holdover oscillator 49 EOAM section 50 User network

Furthermore, holdover switching unit 47, when an abnormality of the equipment or the transmission line is detected by EOAM unit 49 switches the operation from the timing reproducing mode in holdover mode. The period of the control packet is ITU-T Y. 1731 or IEEE 802.1ag recommendation.

A wireless transmission apparatus according to the present invention is made to solve the above-described problem. A wireless frame in which a LAN signal including a timing packet and an error detection code are multiplexed and converted into a high-frequency wireless output signal is provided. The radio frame error rate is calculated by receiving and demodulating from the radio transmission path, separating the LAN signal from the demodulated radio frame, and detecting a radio frame signal error from the error detection code in the radio frame. When the radio frame error rate calculated by the radio receiver and the radio receiver exceeds a first threshold, the clock and timing pulse are generated based on the period and phase reproduced from the timing packet included in the LAN signal. From the timing playback mode to be output, it is based on the cycle and phase saved during normal operation. The holdover mode to output a click and timing pulses, a radio transmission apparatus characterized by comprising, a holdover switching unit for switching the operation mode.

The radio transmission method according to the present invention is a radio transmission method in a radio transmission apparatus, in which a radio reception unit multiplexes a LAN signal including a timing packet and an error detection code, and converts it into a high-frequency radio output signal. The radio frame is received and demodulated from the radio transmission path, the LAN signal is separated from the demodulated radio frame, and the signal error of the radio frame is detected from the error detection code in the radio frame. A step of calculating a rate and a period and phase reproduced from a timing packet included in the LAN signal when the holdover switching unit has a radio frame error rate calculated by the radio reception unit exceeding a first threshold value; Normal operation from timing recovery mode that outputs clock and timing pulse based on The holdover mode for outputting the clock and timing pulses on the basis of the cycle was saved and phase, a radio transmission method characterized by comprising the steps of: switching the operating mode.

According to the first embodiment of the present invention, a radio frame is demodulated from a radio output signal received from a radio transmission path, a radio frame error rate is calculated from an error detection code in the demodulated radio frame, and the radio frame error is calculated. If the rate exceeds the first threshold value, the process proceeds from the timing reproducing mode in holdover mode. Thereby, the wireless transmission device can detect the abnormal state in a short time after the occurrence of the abnormality in the device or the transmission line without executing the EOAM control, and can maintain the accuracy of the clock frequency and the time.

As described above, the wireless transmission device 40a receives the radio frame from the radio transmission path 30 and demodulates the radio frame that is multiplexed with the LAN signal including the timing packet and the error detection code and converted into the radio output signal of high frequency, The radio signal is calculated by the radio receiving unit 41a and the radio receiving unit 41a that separates the LAN signal from the demodulated radio frame and detects a radio frame signal error from the error detection code in the radio frame to calculate the radio frame error rate. When the received radio frame error rate exceeds the threshold B, it is stored in a normal state from the timing recovery mode in which the clock and timing pulse are output based on the period and phase recovered from the timing packet included in the LAN signal. A clock and timing pulse output based on period and phase To-over mode, it includes a hold-over switching unit 46 for switching the operation mode, the.

With this configuration, the radio frame is demodulated from the radio output signal, the radio frame error rate is calculated from the error detection code in the demodulated radio frame, and when this radio frame error rate exceeds the threshold B, the timing reproduction is performed. It switched from mode to the Hall-over mode. As a result, the wireless transmission device 40a can detect an abnormal state in a short time after the occurrence of an abnormality in the device or the transmission line without executing the EOAM control, and shift to the holdover mode. The accuracy of frequency and time can be maintained. Further, the wireless transmission device 40a need not include a compensation oscillator.

Further, the wireless reception unit 41a measures the reception power of the wireless output signal received from the wireless transmission path 30, and the holdover switching unit 46, when the reception power measured by the wireless reception unit 41a falls below the threshold A, from the timing reproducing mode in holdover mode, it switches the operation mode.

This configuration is measured received power of the radio output signal, when the received power is below the threshold value A, switched from the timing reproducing mode in holdover mode. As a result, the wireless transmission device 40a can shift to the holdover mode in a short time after the occurrence of an abnormality in the device or the transmission line without executing EOAM control, and maintains the accuracy of the clock frequency and the time. be able to.

In addition, the wireless receiver 41a detects a timing packet used for clock frequency and time synchronization from a LAN signal separated from a wireless frame, and detects a signal error based on a redundant code in the packet of the LAN signal. It includes a packet switch unit 42 for calculating a packet error rate, holdover switching unit 46, if the packet error rate calculated by the packet switch unit 42 exceeds the threshold value from C, timing recovery mode in holdover mode, operation Switch modes.

With this configuration, signal error based on redundant code in the LAN signal packet is detected, the packet error rate is calculated, when the packet error rate exceeds the threshold C, holdover mode from the timing recovery mode Switch to. As a result, the wireless transmission device 40a can shift to the holdover mode in a short time after the occurrence of an abnormality in the device or the transmission line without executing EOAM control, and maintains the accuracy of the clock frequency and the time. be able to.

Further, the holdover switching unit 46 determines that the radio frame error rate is equal to or lower than the threshold value B, the received power is equal to or higher than the threshold value A, the packet error rate is equal to or lower than the threshold value C, and the timing packet normal reception conditions are all satisfied. , the timing recovery mode from the hold-over mode, switches the operation mode.

With this configuration, a radio frame error rate is less than the threshold B, the received power threshold A or more, the packet error rate is less than the threshold value C, and, if the conditions of the normal timing packet reception are all met, the timing recovery from holdover mode Switch to mode. Thus, the radio transmission device 40a does not execute the EOAM control, it is possible to accurately transition holdover mode and timing recovery mode, it is possible to maintain the accuracy of the clock frequency and time.

As described above, the wireless transmission device 20b and the wireless transmission device 40b are wireless transmission devices employing an adaptive modulation scheme. Holdover switching unit 46 of the radio transmission device 40b, when the switching of the modulation scheme due to adaptive modulation occurs, switch certain time the operation mode to holdover mode, further, when the modulation scheme is a fixed time stable, the operating mode Switch to the timing playback mode.

With this configuration, if the switching of the modulation scheme due to adaptive modulation occurs, switch certain time the operation mode to holdover mode, if the predetermined time modulation scheme is stabilized, it switches the operation mode to the timing recovery mode. As a result, the wireless transmission device 40b can shift to the holdover mode in a short time after an abnormality occurs in the device or the transmission line without executing EOAM control, and the clock frequency and time accuracy can be improved. Can keep.

Claims (10)

A LAN signal including a timing packet and an error detection code are multiplexed and a radio frame converted into a high-frequency radio output signal is received and demodulated from the radio transmission path, and the LAN signal is separated from the demodulated radio frame. A radio reception unit that calculates a radio frame error rate by detecting a signal error in the radio frame from an error detection code in the radio frame;
Timing reproduction mode for outputting a clock and a timing pulse based on a period and a phase reproduced from a timing packet included in the LAN signal when a wireless frame error rate calculated by the wireless reception unit exceeds a first threshold value And a holdover switching unit that switches the operation mode to a holeover mode that outputs a clock and a timing pulse based on a period and a phase stored in a normal state. The wireless reception unit measures received power of a wireless output signal received from the wireless transmission path;
The wireless transmission according to claim 1, wherein the holdover switching unit switches an operation mode from the timing recovery mode to the holeover mode when the reception power measured by the wireless reception unit falls below a second threshold. apparatus. By detecting a timing packet used for clock frequency and time synchronization from a LAN signal separated from a radio frame by the wireless receiver, and detecting a signal error based on a redundant code in the packet of the LAN signal, A packet switch unit for calculating the packet error rate is provided.
The holdover switching unit switches an operation mode from the timing regeneration mode to the holeover mode when a packet error rate calculated by the packet switch unit exceeds a third threshold. The wireless transmission device according to claim 1 or 2. A normal determination process of the timing packet detected by the packet switch unit that calculates the packet error rate by detecting a signal error based on a redundant code in the packet of the LAN signal separated from the wireless frame by the wireless receiving unit. A timing processing unit to be executed,
The holdover switching unit includes the packet error rate calculated by the packet switch unit when the error rate of the radio frame is equal to or less than the first threshold, the received power measured by the radio reception unit is equal to or greater than a second threshold. 2. The wireless transmission device according to claim 1, wherein the operation mode is switched from the hole-over mode to the timing recovery mode when all of the conditions for the normal reception of the timing packet and the timing packet normal reception are satisfied.   The holdover switching unit switches the operation mode to the hole-over mode for a certain period of time when the modulation system is switched by adaptive modulation, and further switches the operation mode to the timing recovery mode when the modulation system is stable for a certain period of time. The wireless transmission device according to claim 1, wherein the wireless transmission device is switched. A wireless transmission method in a wireless transmission device,
The wireless reception unit receives a radio frame multiplexed with a LAN signal including a timing packet and an error detection code and converted into a high-frequency radio output signal, demodulates the radio frame, and transmits a LAN signal from the demodulated radio frame. And calculating a radio frame error rate by detecting a radio frame signal error from an error detection code in the radio frame;
When the holdover switching unit has a radio frame error rate calculated by the radio reception unit exceeding a first threshold value, a clock and a timing pulse based on a period and a phase reproduced from the timing packet included in the LAN signal And a step of switching the operation mode from a timing reproduction mode for outputting a clock to a hall-over mode for outputting a clock and a timing pulse based on a period and phase stored in a normal state. The wireless receiving unit measuring received power of a wireless output signal received from the wireless transmission path;
The wireless transmission according to claim 6, wherein the holdover switching unit includes a step of switching from the timing recovery mode to the holeover mode when the received power measured by the wireless reception unit falls below a second threshold. Method. The packet switch unit detects a timing packet used for clock frequency and time synchronization from the LAN signal separated from the radio frame by the radio reception unit, and detects a signal error based on a redundant code in the packet of the LAN signal. Detecting a step of calculating a packet error rate;
The holdover switching unit includes a step of switching the operation mode from the timing regeneration mode to the holeover mode when the packet error rate calculated by the packet switch unit exceeds a third threshold value. The wireless transmission method according to claim 6 or 7. Timing packet detected by a packet switch unit that calculates a packet error rate by detecting a signal error based on a redundant code in a packet of a LAN signal separated from a radio frame by the radio reception unit by the timing processing unit Executing the normality determination process of
The packet error rate calculated by the packet switch unit when the holdover switching unit calculates an error rate of the radio frame equal to or lower than the first threshold, and a received power measured by the radio reception unit equals or exceeds a second threshold. And a step of switching the operation mode from the hole-over mode to the timing recovery mode when all the conditions for normal reception of timing packets and all the conditions for timing packet normal reception are satisfied. Method.   The holdover switching unit switches the operation mode to the hole-over mode for a fixed time when the modulation method is switched by adaptive modulation, and further switches the operation mode to the timing recovery mode when the modulation method is stable for a fixed time. The wireless transmission method according to claim 6, further comprising a switching step.

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